1. Field of the Invention
The present invention relates to an electronic component feeding apparatus for feeding electronic components to an electronic component mounting apparatus.
2. Description of Related Art
Electronic components in the form of chips constituting electronic circuits (hereinafter referred to as electronic components) have recently come into wide use, and as there have been more and more various types of electronic components, the number of type and quantity of electronic components mounted on one electronic circuit has been increased. Such a variety of electronic components are mounted in certain combinations onto a printed circuit board with the use of an electronic component mounting apparatus. To feed the electronic components to the electronic component mounting apparatus at desired timings, an electronic component feeding apparatus is desired to operate at a high speed and to be highly reliable.
A conventional electronic component feeding apparatus will be explained by referring to FIGS. 4 to 6.
Referring to FIG. 4, component feeder units 1 of the conventional electronic component feeding apparatus conveys electronic components assemblies 2 intermittently in a direction of (b) at regular intervals of a given pitch by reciprocating pivotal movements of a feed lever 4, each of the electronic components assemblies 2 accommodating a row of electronic components 7 held on a tape-like carrier (FIG. 6). A plurality of component feeder units 1 are loaded on a component supply table 3 in such a way that the component supply units 1 can be moved in a direction of (a) to be transferred to a feeding position (d) shown in FIG. 5. The feed lever 4 of the component feeder unit 1 which is brought to locate at the feeding position (d) is driven by a transmission mechanism 41.
The component feeder unit 1 includes a frame structure 31 having a mounting unit for anchoring it to the component supply table 3, and a loading unit 32 for loading the tape-like electronic components assembly 2 thereon, and a guide 36 for guiding the electronic components assembly 2. The feed lever 4 is pivotally mounted around an axial point 34 on the frame structure 31 and is driven by the pressing action of the transmission mechanism 41 for swinging motion between a lower limit of a pressing roller 42 of the transmission mechanism 41 and an upper limit thereof defined by an upper stopper (not shown). The component feeder unit 1 is further provided with a reel-out unit 33 for intermittently feeding the electronic components assembly 2 in the forward direction (b) via a link 37 by the reciprocating motion of the feed lever 4 and a separating unit 38 for peeling off and taking up a covering tape 20 (FIG. 6) from the electronic components assembly 2. A tape holder 5 retains the electronic components assembly 2 from lifting up after separation of the covering tape 20, and prevents the electronic components 7 from popping out therefrom, having a shutter 6 disposed at its tip where the electronic components 7 are picked up, which opens and closes in synchronism with the reciprocating swing motion of the feed lever 4.
The feed lever 4 has a spring (not shown) upwardly urging a contacting portion 16 at the upper end of the feed lever 4, by which the feed lever 4 remains in pressed contact with the upper stopper when the contacting portion 16 is disengaged from the pressing roller 42. The stroke of the reciprocating swing motion of the contacting portion 16 between its upper and lower limits is the length of an effective stroke which is defined by the pitch for intermittently feeding the electronic components assembly 2 in the forward direction (b). The component supply table 3 carries a plurality of the component feeder units 1, each having different effective strokes of the feed lever 4.
The transmission mechanism 41 comprises a driving arm 43 for swinging movements along a direction of (e), the pressing roller 42 mounted at the distal end of the driving arm 43 for pressing down the contacting portion 16 of the feed lever 4, and a driving means (not shown) for carrying the driving arm 43 to reciprocate in a swing motion at a predetermined swinging angle. The pressing roller 42 is driven at a constant stroke of the pressing motion.
The procedure of feeding the components in such an electronic component feeding apparatus will now be explained.
Referring to FIGS. 3 and 4, the effective stroke of each feed lever 4 is preliminarily set corresponding to respective feeding pitch of the electronic components assembly 2 for conveying the electronic components 7. The effective stroke for each feed lever 4 is differently set in respective component feeder unit 1 by adjusting the position of the stopper which defines the upper limit, while the lower limit is set to be a fixed position of the lower dead point of the pressing roller 42 for all the component feeder units 1. In particular, the upper limit of the feed lever 4 is set to a higher position for a component feeder unit 1 having a greater feeding pitch, i.e., the effective stroke, as can be seen from the vertical motion of the feed lever 2 shown by a double-dotted chain line in FIG. 3. And the upper limit of the feed lever 4 is set to a lower position for a component feeder unit 1 having a shorter effective stroke, as can be seen from the vertical motion of the feed lever 1 shown by a solid line in FIG. 3.
As the pressing roller 42 is lowered, it comes into direct contact with the contacting portion 16 of the feed lever 4 located at its upper limit and presses it down by the length of the effective stroke until its lower limit. When the feed lever 4 is returned upward by the yielding force of the spring together with the pressing roller 42, the electronic components assembly 2 is advanced by the predetermined pitch along the direction (b). The electronic components assembly 2 is guided into the tape holder 5, after its covering tape 20 is peeled off at the separating unit 38 before the shutter 6. The lower limits of the pressing roller 42 and the feed lever 4 are set to be identical for all the component feeder units 1, as described above and as can be seen from the vertical motion of the pressing roller 12 shown by solid and broken lines in FIG. 3.
The operation of the shutter 6 is linked to the vertical movements of the feed lever 4, and the shutter 6 opens and closes as the feed lever 4 descends and ascends, respectively. A nozzle C of the electronic component mounting apparatus B is lowered as the shutter 6 opens and picks up an electronic component 7 under the opened shutter 6 by a sucking action. The nozzle C is lifted before the shutter 6 is closed and transfers the electronic component 7 to a mounting position for mounting it on a printed circuit board A.
While the pressing roller 42 stays at its upper dead point, the component supply table 3 conveys the component feeder unit 1 loaded with a desired type of electronic components 7 to the feeding position (d). By repeating these actions, the electronic component feeding apparatus supplies a set of electronic components 7 to the electronic component mounting apparatus B according to a predetermined program.
When the transmission mechanism 41 is placed in operation, specifically when the descending pressing roller 42 comes into direct contact with the contacting portion 16 of the feed lever 4, a certain amount of vibration is generated caused by the impact of collision. The amount of vibration depends greatly on the rate of the pressing roller 42 hitting against the contacting portion 16. The speed is, however, fixedly set irrespective of types of the component feeder units 1 having different sizes of components and feeding pitches as shown in FIG. 3.
The electronic components 7 accommodated in the electronic components assembly 2 of which feeding pitch is small are generally light weighted and are more affected by the vibration caused by the impact. When the transmission mechanism 41 is operated at a higher speed in case that a component feeder unit 1 having small feeding pitch and the one having a greater feeding pitch are carried on the component supply table 3, the electronic component 7 positioned at the shutter 6 of the component feeder unit 1 with a small feeding pitch receives a greater shock by the hitting rate of the feed lever 4, causing the electronic component 7 to bounce or jump out of the place while the shutter 6 is opened. This causes the nozzle C of the electronic component mounting apparatus B to fail in picking up the electronic component 7, to drop the electronic component 7 during the transfer by insufficient sucking force, or to mount the electronic component 7 at an incorrect position.
The speed of feeding the electronic components 7 can thus be only increased up to a limited degree which is defined by the effects of the vibration to a light weighted type electronic components.